Automobiles are mass-produced along assembly lines, in which the various systems and components that make up an automobile are joined together using human and/or robot controlled tools. Oftentimes, different sheet metal pieces are joined together in order to form a desired component. For instance, “tailor-welded blanks” are formed by joining together, such as for instance by laser welding, two or more steel blanks of different compositions and/or different thicknesses. After the welded-blanks have been cold-pressed, components are obtained having properties of mechanical strength, pressability and impact absorption that vary within the components themselves.
In order to provide improved corrosion resistance, it is common to fabricate such blanks using coated sheet-metal materials, such as for instance boron steels with an aluminum-silicon or a zinc pre-coating surface layer. Unfortunately, the process of laser welding together the pre-coated sheet metal plates results in the formation of a weld joint that is devoid of anti-corrosion protection. Over time, exposure to water, road salt, etc. leads to corrosion along the weld joint and concomitant loss of weld integrity. Loss of weld integrity can lead to separation of the sheet metal plates along the weld joint, resulting in failure of the entire component.
In addition, for hot-stamped components that are fabricated from boron steel, such as Usibor material, the disruption of the AlSi layer along the weld joint causes scaling along the weld joint during subsequent hot-stamping processing.
The prior art solution to this problem involves applying a primer layer to cover the weld joint, and then painting the component to provide a physical barrier from the ambient environment. Unfortunately, the corrosion protection that is provided by the paint layer is inferior to the original coating since the bonding of the paint layer to the base metal is weak. In addition, the paint layer may become damaged over time, allowing water, road salt etc. to come into contact with the underlying weld joint. This may happen, for instance, if the paint is scratched or chipped, or if the paint is not applied properly in the first place and therefore fails to adhere to the underlying material. Further, only the exterior surfaces of many components are painted, and as a result corrosion may occur along the inward-facing surface of the weld joint.
It would therefore be beneficial to provide a process and system that overcome at least some of the above-mentioned limitations and disadvantages of the prior art.